JPS6020750Y2 - Boom drive device for concrete pump vehicle - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a boom drive device for a concrete pump vehicle.

FIG. 1 is an overall view showing an example of a concrete pump vehicle. Generally, in such a concrete pump vehicle, the driving of the concrete pumping device 1 and the driving of the boom cylinder 3 that performs the bending and extending operation of the boom 2 are performed by the operation of the engine 4. The amount of concrete discharged by the concrete pumping device 1 is changed by changing the rotational speed of the engine 4.

In the figure, 1' is a concrete pressure hose.

Therefore, in the above, when changing the discharge amount of the concrete pumping device 1, the oil amount and oil pressure of the operating hydraulic system of the boom cylinder 3 that operates the boom 2 are also changed due to a change in the rotation speed of the engine 4. This causes a change in the speed and force of the boom 2. In particular, when the speed of the boom 2 changes, it becomes difficult to operate, and there is a risk that the boom 2 may collide with a structure or a worker.

For this reason, in the conventional art, as shown in FIG. 2, the hydraulic pressure flow path a of the boom cylinder 3 is closed.

a flow control valve c configured to restrict the return flow rate of pressure oil to b;
d is provided to adjust the speed of the boom 2.

However, in the conventional system described above, the speed is adjusted by releasing pressure using the flow rate control valves C and d, which causes pressure loss.Therefore, an extra-sized hydraulic pump is required, and the driving fuel for the engine 4 is There is a problem that the cost increases and it becomes very uneconomical, and as shown in Figure 3, when the engine speed decreases, the hydraulic pressure suddenly decreases as shown by curve e, so the boom force also decreases. had.

This invention was made to solve the above-mentioned conventional problems.
The discharge side piping of a hydraulic pump driven by an engine is branched into two directions, one of which is guided to a boom cylinder via an electromagnetic switching valve, and the other is guided to an electromagnetic on-off valve via a flow rate adjustment valve with pressure compensation. This invention relates to a boom drive device for a concrete pump vehicle, characterized in that it is provided with a signal generating device that detects when the rotational speed of the engine reaches a predetermined value and issues a signal to switch the electromagnetic on-off valve. be.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 4 shows an example of the present invention, in which the discharge side piping 6 of the hydraulic pump 5 operated by the engine 4 in the concrete pump truck shown in FIG. It is connected to the boom cylinder 3 via the switching valve 8, and the other pipe 9 is connected to the pressure compensated flow rate regulating valve 1.
0 to the electromagnetic on-off valve 11.

Reference numeral 12 indicates a safety valve provided in the middle of the discharge side piping 6, and reference numeral 13 indicates an oil tank.

Further, in order to control the rotational speed of the engine 4 via the governor 14, a control lever 15 provided in the control room of a concrete pump vehicle, for example, is configured to control the engine 4 to a predetermined rotational speed depending on the operating angle of the control lever 15. A signal generator 17 is provided which detects that the electromagnetic opening/closing valve 1 has been reached and generates a signal 16.
1 switching.

In the above configuration, in order to increase the amount of concrete discharged from the concrete pumping device 1 shown in FIG.
When the rotational speed of the engine 4 is increased above the fixed rate operation via the regulator 14 by changing the operating angle of the hydraulic pump 5, the amount of oil discharged from the hydraulic pump 5 to the discharge side piping 6 increases, and the electromagnetic on-off valve 11 increases. Since the oil is in the closed state as shown in FIG. 4, the oil is supplied directly to the boom cylinder and cylinder 3 side, so the amount of oil flowing through the pipe 7 also increases as shown in FIG. 5. It turns out.

However, when the rotational speed of the engine 4 reaches a predetermined value A (Fig. 5), the signal generator 17 detects it depending on the operating angle of the operating lever 15 and issues a signal 16. As shown in (a) above, the pressure-compensated flow rate regulating valve 10, which is set to always release the increased amount B of the oil amount at the rotation speed A, is used to control the increased amount B. Oil is returned to the oil tank 13 via the electromagnetic on-off valve 11.

Therefore, the amount of oil flowing through the pipe 7 returns to the initial amount as shown in FIG.

When the rotational speed of the engine 4 is further increased, the amount of oil flowing through the pipe 7 also increases.

However, since the increased oil amount B is released by the valves 10 and 11 while the oil amount is increasing, it is possible to set the point A to be located in the center of the operating speed range of the engine 4. , the flow rate change range C in the pipe 7 is shown by a dotted line, which is about 172 of the range C' in the conventional case without a flow rate adjustment valve.
It can be done.

By narrowing the range of change in the amount of oil in the pipe 7 in this way, changes in the operating speed of the boom 2 can be reduced, making it easier to operate the boom 2 and improving safety. can.

Furthermore, since pressure loss can be eliminated, the hydraulic pump 5
It is possible to reduce the size of the engine and reduce fuel consumption.

Note that the present invention is not limited to the above-mentioned embodiments, and the signal generating device may be one that emits a signal when the engine rotational speed reaches a predetermined value. It is also possible to have a pressure-compensated flow rate adjustment valve and an electromagnetic on-off valve as one set, so that oil can be released multiple times in stages and the flow rate can be adjusted in stages. Of course, various modifications may be made without departing from the gist of the thin ice invention.

According to the boom drive device for a concrete pump vehicle of the present invention described above, the following excellent effects can be achieved.

([) When the engine speed reaches a predetermined value, a portion of the oil that operates the boom cylinder is released to adjust the flow rate, so changes in boom speed can be reduced. The boom becomes easier to operate.

(11) Since the operability of the boom is improved, safety can also be improved.

(zrr) Compared to the conventional case where a flow control valve is provided in the middle of the piping of the boom cylinder, pressure loss can be eliminated.

(IV) Since there is no pressure loss, the hydraulic pump can be made smaller, and therefore fuel efficiency can be improved.

Since it is equipped with a flow regulating valve with M pressure compensation, the force of the boom can always be kept constant.

[Brief explanation of the drawing]

Fig. 1 is an overall explanatory diagram showing an example of a concrete pump vehicle, Fig. 2 is an explanatory diagram showing a conventional boom speed adjustment method, Fig. 3 is a diagram showing the relationship between engine speed and hydraulic pressure, and Fig. 4 is an explanatory diagram showing the conventional boom speed adjustment method. The figure is an explanatory diagram showing one embodiment of the present invention, and FIG. 5 is a diagram showing the relationship between the engine rotation speed and the oil flow rate to the boom cylinder according to the present invention. 1 is a concrete pumping device, 2 is a boom, 3 is a boom cylinder, 4 is an engine, 5 is a hydraulic pump, 6 is a discharge side piping, 8 is an electromagnetic switching valve, 10 is a flow rate adjustment valve with pressure compensation,
11 is an electromagnetic on-off valve, 16 is a signal, and 17 is a signal generator.

Claims (1)

[Scope of utility model registration request] The discharge side piping of a hydraulic pump driven by an engine is branched into two directions, one of which is led to a boom cylinder via an electromagnetic switching valve, and the other is guided to an electromagnetic on-off valve via a pressure-compensated flow rate adjustment valve, and A boom drive device for a concrete pump vehicle, characterized in that a signal generating device is provided that detects when the rotational speed of the engine reaches a predetermined value and generates a signal for switching the electromagnetic on-off valve.